顶空薄膜微萃取-表面增强拉曼光谱法快速检测枸杞子中的二氧化硫残留量

目的：结合顶空薄膜微萃取技术具有的本底基质干扰小、萃取效率高的优点和表面增强拉曼光谱技术具有的检测快速、灵敏的特点，拟实现枸杞子中二氧化硫残（SO₂）留量的快速分析。方法：在1个10 mL密闭的顶空瓶中放置1.0 g粉碎的枸杞子样品并加稀硫酸酸化，将一片氧化锌（ZnO）薄膜放置在密闭的顶空并于55℃萃取10 min。顶空萃取结束后取出ZnO薄膜，于ZnO薄膜上加入10 μL浓缩的金胶后，采用便携式拉曼光谱仪进行检测。结果：在654 cm^-1可以检测到SO₂清晰明显的拉曼光谱特征峰。实验研究了影响萃取效率的因素，包括萃取时间、萃取温度、相比等。在优化的条件下，该方法的线性范围为25~800 mg·kg^-1，检测下限为15 mg·kg^-1。顶空薄膜微萃取-表面增强拉曼光谱检测枸杞子中SO₂含量的实验结果与传统的碘滴定法所测得的结果不存在显著性差异，加标回收率在83.7%~107.3%范围内。结论：该方法可实现枸杞子中SO₂残留量的快速分析。

Objective:Combined the advantage of low background interference and high extraction efficiency for headspace thin-film microextraction sample preparation technique with the advantage of fast detection and high sensitivity for surface-enhanced Raman spectroscopy (SERS), an approach had been developed for the rapid detection of residual sulfur dioxide in Lycii fructus. Methods:1.0 g of crashed Lycii fructus was put in a 10 mL glass vessel and then was acidized by diluted sulphuric acid. A ZnO film was hung in the head space of the sealed glass vessel to extract SO₂ from the sample solution at 55℃ for 10 mins. After the extraction, the ZnO film was taken out and 10 μL of concentrated AuNPs was dropped onto its surface for SERS analysis. All SERS measurements were carried out by a portable Raman spectrometer. Results:A characteristic peak for SO₂ can be detected at 654 cm^-1. Experimental parameters related to extraction efficiency including extraction time, extraction temperature and phase ratio were investigated and optimized. Under the optimized conditions, a good linearity was in the range of 25-800 mg·kg^-1 and the detection limit was 15 mg·kg^-1. There was no significant difference between the developed method and the traditional distillation and titration method for the determination of SO₂ in Lycii fructus, and the recoveries were in the range of 83.7%-107.3%. Conclusion:The developed method coupled with headspace thin-film microextraction and surface-enhanced Raman spectroscopy can be used for quick determination of residual sulfur dioxide in Lycii fructus.

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